The present invention relates generally to lightning testing of electronic equipment. More particularly, the present invention relates to a circuit for generating a sequence of high energy radio frequency (RF) pulses for use in lightning testing.
In certain electronic industries, for example the aviation electronics (avionics) industry, it is frequently necessary to lightning test electronic equipment to verify that the equipment will remain operational after a lightning strike. Testing for lightning induced multiple-burst transient susceptibility presents several problems. In addition to the difficulty of being capable of applying high voltage pulses to electrical cabling connected to the electronic equipment under test, the lightning test circuitry must in some instances be capable of providing as many as 24 or more RF pulses within a short period of time, for example during as little as a two second period. Designing a transient pulse generator which is capable of handling high voltage potentials and which can provide many transient pulses in a short period of time has proven problematic.
A transient pulse generator, for generating high energy RF pulses for lightning testing electronic equipment, generates control pulses. An insulated gate bipolar junction transistor (IGBT) is coupled to the conducts in response to the control pulses. A first capacitor is coupled to an electrode of the IGBT and to a first voltage potential. A transformer has its primary coupled between the first capacitor and a second electrode of the IGBT such that when the IGBT is not conducting the first capacitor is charged to a difference between the first and second voltage potentials. When the IGBT is switched into conduction mode the first capacitor discharges across the primary of the transformer, resulting in generation of a pulse across the secondary of the transformer. A second capacitor is coupled between a third voltage potential and an injection core which provides magnetic coupling to the equipment to be tested. The second capacitor charges to substantially the third voltage potential between control pulses. A spark gap device has a trigger electrode coupled to the secondary of the transformer, an adjacent electrode coupled to third voltage potential and to the second capacitor, and an opposite electrode coupled to ground such that a pulse generated across the secondary of the transformer triggers the spark gap thereby discharging the second capacitor and providing a high energy RF pulse to the injection core for coupling to the electronic equipment.